Semiconductor devices based on nitride semiconductor can improve the tradeoff between breakdown voltage and on-resistance. Thus, lower on-resistance and higher breakdown voltage can be achieved beyond devices based on silicon (Si). In general, in semiconductor devices based on gallium nitride (GaN), a phenomenon called current collapse may occur and result in increasing the on-resistance. Current collapse is a phenomenon of current decrease under application of high electric field. To avoid this phenomenon requires dispersing the electric field inside the device. For instance, the electric field inside the device is dispersed by ingeniously designing the surface structure of the semiconductor device.
In such a semiconductor device based on nitride semiconductor, further stabilization in characteristics is desired.